What is a Fluency Disorder?


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Most people experience disfluencies while speaking from time to time. However, if disfluencies are the norm, then the cause may be a fluency disorder. A fluency disorder is an interruption in the flow of speaking, characterized by atypical rate, rhythm, and disfluencies. The two main types of fluency disorders are stuttering and cluttering. Fluency disorders cannot only make it difficult for someone to communicate with others effectively, but they can also cause psychological, emotional, and social challenges.


Stuttering is the most common fluency disorder. It affects about five percent of children and less than one percent of adults in the U.S. Stuttering occurs when a person says a whole word or part of a word more than once. This disfluency may result in repetitions (D-d-d-dog), prolongations (Mmmmmilk), or blocks, which is when a person has a hard time getting a word out.

The most common type of stuttering is developmental stuttering, which typically begins in childhood as kids learn to put more complex words together. It usually starts gradually, affecting single words. As the disorder progresses, dysfluencies become more frequent and may begin to affect complete phrases.

There have been many theories as to why people stutter, but the exact cause remains unknown. What we do know is that stuttering has been linked to high levels of dopamine, a neurotransmitter associated with pleasure and reward.

In addition, many people who stutter also have a family member who stutters, suggesting there is a genetic component. There also may be minor brain differences, such as brain asymmetries in the areas responsible for verbal communication, that contribute to these speech disfluencies.


Like stuttering, cluttering usually begins in childhood. Cluttering is a fluency disorder that is characterized by rapid, unclear, and disorganized speech. Key signs of cluttering include speaking fast and jamming words together. Even when the speaker is not speaking faster than average, they are still speaking too quickly for their system to handle.

Someone who clutters may blend syllables together, add filler words (i.e., um, uh, and er), and pause in places that make their speech sound jerky.

Disorganized speech planning, being unsure of what to say, and talking too fast may cause cluttering.

Signs of a Fluency Disorder

People with a fluency disorder may develop certain behaviors to avoid speaking or hide their disfluencies. They might cover their mouth, pretend to cough or yawn, rearrange words in a sentence, or use filler words in an attempt to make their speaking rate sound normal. Some people struggling with a fluency disorder may even avoid speaking altogether, avoid certain words, or pretend to forget what they were going to say.

Treating Fluency Disorders

While it is not always the case, fluency disorders can co-occur with other conditions, including attention-deficit/hyperactivity disorder (ADHD), autism, and learning disabilities. They are further complicated by the fact that some people both stutter and clutter their words. However, many of the treatments used to treat one fluency disorder can also help with the other.

Vivera recognizes the unique needs of those living with fluency disorders, like stuttering and cluttering. Through our Neurosciences Division, we are dedicated to the research and development of effective treatments for those affected by such disorders.

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